Early Cretaceous continental-scale sediment dispersal: Towards resolving the McMurray conundrum - Discussion

Abstract

Wahbi et al. (2025) addresses aspects of the oilsands-hosting McMurray Formation (Fm) in northeast Alberta, Canada. As one of the largest petroleum reservoirs on Earth, resolving the geology of the McMurray Fm has potentially wide-ranging economic implications, and so the interval has received significant research attention. As noted by Wahbi et al. (2025), differing interpretations of the McMurray Fm stem largely from varying assessments of the degree of marine influence, and this is commonly referred to as the “McMurray conundrum” (Gingras and Leckie 2017; Gingras et al. 2019). At its core, the McMurray conundrum describes the seemingly irreconcilable juxtaposition of: 1) fluvial architectures (point bars and channel belts) that are associated mainly with the C2 through A2 parasequences and some evidence that the regional parasequences were deposited in freshwater (terrestrial) environments; versus 2) the preservation of bioturbation in both sand beds and the mudstone layers that drape point bar surfaces (i.e., inclined heterolithic stratification) coupled with the minimal preservation of terrestrial strata (e.g., floodplain deposits, coal beds, and paleosols).